The present invention relates to a vulcanization apparatus for cylindrical rubber moldings.
A vulcanizer is a part of the typical conventional vulcanization apparatus. In a known type of vulcanizer, rubber moldings are placed inside a vulcanization vessel, and then high temperature and high pressure steam is introduced into the vessel to effect vulcanization.
FIG. 3 illustrates a prior art apparatus for vulcanizing a cylindrical rubber molding 61, such as a belt material prior to being cut crosswise into final belt products, including a vulcanizer vessel 50. When the molding 61 is completely molded over the external circumference of a hollow cylindrical mold 62, flanges 63 and 64 are mounted, as illustrated, on both ends of the mold 62, and then a rubber sleeve 65 is placed over the assembly. Thus the sleeve 65 covers the flanges 63 and 64 and the molding 61. Then the molding 61 in this state is placed on a table 51 inside the vulcanizer vessel 50. High temperature steam is then introduced from a steam pipe (feed pipe) 52, and high temperature and high pressure steam is introduced from a steam pipe (feed pipe) 54, while steam-liquid is drained and recovered from steam pipes (discharge pipes) 53 and 55. The molding 61 is heated by the steam through thermal conduction via the circumferential walls of the mold 62 and the sleeve 65, and at the same time, the molding 61 is pressed against the external circumference of the mold 62 by the sleeve 65; thus the entire molding 61 is vulcanized at once.
In the vulcanization system using the foregoing vulcanizer, the reason for placing a rubber sleeve 65 over the external circumference of a molding is to prevent steam from directly contacting the molding. In the conventional system as mentioned above (see FIG. 3), the success or failure of vulcanization depends solely on the closeness of contact between the rubber sleeve 65 and the flanges 63, 64, and there is a high risk of contact between steam and the molding. If dirt particles are caught when the sleeve 65 is being placed over the flanges, or if the elasticity of the sleeve is reduced after repeated use, the close contact between the sleeve and the flanges will be defective, and steam will penetrate through a gap thus generated. If steam penetrates into the sleeve and contacts the molding, sulfur, etc. from the molding might be present in the drain steam-liquid to be recovered, and in turn might corrode or damage the steam generator (such as a boiler). Furthermore, the molding will suffer adverse effects due to exposure to steam, in physical properties of the rubber, adhesion of the rubber and composite materials (such as cords in the belt).
For rubber moldings with a larger circumference, in addition to the aforementioned system with the vulcanizer, other vulcanization systems are also available wherein moldings are placed across a pair of pulleys and moved longitudinally in sequence to achieve heating and pressurization (e.g. continuous vulcanization systems such as the press type and rotary curing press). Such systems, however, are troublesome in that unvulcanized moldings of low strength must be removed from molds and placed across the press, and it takes a long time to vulcanize the whole circumference. Moreover, such systems are hardly applicable to moldings with shorter circumference (such as those used to form fan belt materials for vehicles).